Introduce a stack for variables not closed over.
Make the stack a SIMPLE-VECTOR, manage the fill-pointer as a special variable.
Remove some debugging output.
Establish stacks as necessary.
Remove a temporary code note.
LET: Don't confuse binding context with enclosing context wrt. the stack.
Specialize STACK-REF over the stack nesting depth.
Add a (wrong) definition of LOAD-TIME-VALUE.
Merge branch 'master' into stack

Conflicts:
	sb-eval2.lisp
LAMBDA: Bail out on complex lambda lists.
Conflicts:
	sb-eval2.lisp
Fix indentation.
PREPARE-GLOBAL-CALL: Deal with redefinition by using FDEFINITION-OBJECTs.
Conflicts:
	sb-eval2.lisp
Simplify PREPARE-LAMBDA to rely on &MORE optimization.
Implement lambda-lists properly.
PREPARE-LAMBDA: Stack-allocate environments instead of managing a stack.
PREPARE-LAMBDA: Support &KEY ((:keyword var) ...) syntax.
Remove explicit stack management.
PREPARE-LAMBDA: Simplify.
Merge branch 'stack'

Conflicts:
	sb-eval2.lisp
Add a small missed optimization.